The 3-wire IAC valve - Operation - Testing - Maintenance

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Here I am talking about the IAC of 3 cables, toyota model. How to perform tests, with tester, multimeter measurement and electrical diagram that will let them know if it works or not.

3-wire IAC valves toyota.

How does it work?

I will explain the operation for IAC 3 cables models after 2002.

For previous models clic here

These IACs work the same as their predecessors, but with the variant that the control system of the IAC is within the IAC itself. That is, the modulation control circuit for both opening and closing windings are within the IAC. This reduces the size and warming of the main control module, as well as making it less prone to damaging the IAC, compromising the vehicle's computer.

For compatibility, the pins were left as is the previous IAC. But with the caveat that there is only one pin that is subjected to the pulse width modulation (PWM) action as seen in the following figure.

If the computer wants to open the valve, it gives pulses of short duration in ON. To close it is the opposite process, it gives long pulses in ON. In the following figure you can see this behavior in the pulse train.

Pusos PWM IAC 3 cables

The initial wave corresponds to IAC fully open. And the last one corresponds to a totally closed IAC.

Like its predecessor, it also has a spring that puts it in the central position in case of any damage, it takes it to a safe point of operation for the engine (which does not turn off).

It is important to clarify the command signal of this pin must be negative.


How to identify 3-wire IAC cables?

The pins of this connector are 3:




Negative power


Positive power (+ 12V)


Modulated signal to Open the IAC (negative signal)

In the following figure you can see a typical IAC of three cables.

conector iac 3 cables toyota

Identifying the pins of the IAC, is not as simple as the previous IAC of 3 cables. The only thing that can be measured with a multimeter is that all the pins are not communicated. That is, they do not have a resistance lower than 200k ohms between any of them. The power supply is usually identified by placing the ohmmeter on a scale greater than 1 M ohms and measuring the central one with respect to the sides. Whoever has measurement there is feeding the IAC. The procedure is shown below:

Make the measurements as indicated in the image below:

medición iac 3 cables toyota

The measurements should give as what they show in steps 1, 2 and 3. These correspond to the diagram seen to the right of the image, where the central would be the common and the lateral terminals are those that we are going to test.


In this case, the terminals would be as seen in the following table:

Terminal 1

Terminal 2

Terminal 3




How to test the IAC 3 cables?

It's very simple and you do not need a tester for this. already having the terminals identified, we can directly energize the IAC following the following diagrams:

hacer funcionar iac 3 toyota cables con probador

We connect the positive 12V battery to the terminal + B which in this case is the central terminal, and the negative to the GND. You have to see a movement to close everything and then open the IAC. There is no need to pulse through the PWM pin because it will not react unless the frequency exceeds 20hz. If when we energize the IAC, there is movement, it means that the control is working correctly.

Cleaning the IAC 3 cables

Cleaning it consists of pouring solvent into the mechanism of action of the IAC to remove the black soot from the combustion residues. Try as much as possible to place the valve so that the dirty liquid comes out of it so as not to clog the piston or the shaft.

After cleaning everything you can with solvent, if they operate it in the way you teach them, they will make cleaning it much more effective. Since the movement while pouring the solvent removes the soot that is trapped where we can not physically reach with a rag.

I hope you liked this short tutorial, if you have any questions or suggestions, below in the question box you can make them.

A video of how I did these tests:


Questions or suggestions

In the box below questions you can make them.

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Realizado por:


Chica Mecánica

Dennis García.



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    The 3-wire IAC valve - Operation - Testing - Maintenance

    The 3-wire IAC valve - Operation - Testing - Maintenance

    Here I am talking about the IAC of 3 cables, toyota model. How to perform tests, with tester, multimeter measurement and electrical diagram that will let them know if it works or not.

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    • Asked by Jose
      on 02/21/2019
      Buenos días. Muy buenos tus Tutoriales , en Serio explicas muy bien quisiera saber si para ver si el cable de señal sirve, puedo probar continuidad en el cable desconectado la batería porque ese es el problema de mi Vitz , no regula tiene corriente también probé su negativo y nada es como si se quedará en una posición neutra y no regula ni se siente la compensación cuando uso luces o el ventilador o cualquier consumo de energía. Gracias Answer:
      Gracias Jose, trato de hacer la explicación lo más simple que puedo. Depende del modelo, las más viejitas puede hacerse directo con bateria solo el de masa porque la computadora hacia la modulación por separado en las dos lineas. Para las nuevas si puedes hacer la prueba de alimentación (RELE EMS PRINCIPAL No a + de bateria directo) y de masa con batería, pero el cental es modulado.

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